Encyclopedia · chelator
Tetrasodium EDTA
The more alkaline, more soluble EDTA salt, with the same chelating job as disodium EDTA and wide use in clarifying and chelating shampoos.
What it is
Tetrasodium EDTA is the fully neutralised sodium salt of EDTA, more soluble and alkaline than disodium EDTA. It appears in many clarifying and chelating products and in colour and bleach formulations.
How it works
It binds calcium, magnesium, iron and copper ions. It is covered by the same safety assessment as the other EDTA salts (Lanigan 2002).
What the studies show
- A safety assessment of EDTA and its salts found cosmetic skin exposure gives systemic levels far below toxic oral doses, with aerosol inhalation the concern, and the panel found them safe as used (Lanigan 2002).
- Copper-doped white hair produced more hydroxyl radicals under wet UVA than undoped hair in a lab study (Millington 2020).
- In over 300 women from 9 countries, calcium, magnesium and copper rose from root to tip, and those who rated their hair health as poor had higher metal levels (Godfrey 2013).
- Calcium concentrated in the cuticle of coloured hair washed in tap water (Smart 2009).
The hair-benefit evidence is indirect, and we found no clinical trial of an EDTA shampoo on hair outcomes.
Side effects and safety
See disodium EDTA.
Bottom line
The same advice as for disodium EDTA. For coloured or porous hair, use chelating shampoos sparingly (every 2-4 weeks) and follow with conditioner.
Studies 4
Lanigan RS et al. Final report on the safety assessment of EDTA, calcium disodium EDTA, diammonium EDTA, dipotassium EDTA, disodium EDTA, TEA-EDTA, tetrasodium EDTA, tripotassium EDTA, trisodium EDTA, HEDTA, and trisodium HEDTA. 2002
Result: Cosmetic skin exposure gives systemic levels far below toxic oral doses; inhalation from aerosols was the concern; may increase penetration of other chemicals; the panel found EDTA and its salts safe as used.
Read the study ↗Millington KR et al. UV damage to hair and the effect of antioxidants and metal chelators. J Cosmet Sci. 2020
Result: UV damage to hair was affected by antioxidants and metal chelators in the lab.
Read the study ↗Godfrey S et al. Metals in female scalp hair globally and its impact on perceived hair health. 2013
Result: Calcium, magnesium and copper rose from root to tip, and women who rated their hair health as poor had higher metal levels; hardness ions were higher in people who coloured their hair. Unilever-affiliated authors; an association only.
Read the study ↗Smart KE et al. Copper and calcium uptake in colored hair. 2009
Result: Calcium concentrated in the sulfur-rich layers of the cuticle of coloured hair; copper uptake can add to damage during later colouring.
Read the study ↗Related
- Disodium EDTAThe classic cosmetic chelator, which grabs calcium, magnesium, iron and copper so shampoos lather and keep in hard water, with no clinical hair trials of its own.
- Tetrasodium glutamate diacetateA biodegradable, glutamic-acid-based chelator marketed as a greener EDTA replacement, with essentially no hair-specific data.
- Sodium phytateA rice- or corn-derived chelator used in natural shampoos as a preservative booster and iron and copper binder, with no hair trials.
- Citric acidThe most common pH adjuster in shampoos and conditioners and, in a 2025 lab study, a calcium-removing treatment that strengthened chemically treated hair.
- Hard water and hairHard water leaves calcium on hair and can irritate skin, but there is no good human evidence that it causes hair loss, and chelating shampoos are untested in trials.